bcd_express: Run BCD on a subset of frequencies
In multiband: Period Estimation for Multiple Bands

bcd_express runs bcd_inexact on a subset of frequencies determined by Lomb-Scargle fits that is guaranteed to include the minimum.

1 2	bcd_express(tms, sol_ls, omega_seq, gamma1, gamma2, at, max_iter = 100, verbose = FALSE)

`tms`	list of matrices whose rows are the triple (t,m,sigma) for each band.
`sol_ls`	list of lists where sol_ls is output from lomb_scargle
`omega_seq`	vector of freqencies used for producing sol
`gamma1`	nonnegative regularization parameter for shrinking amplitudes
`gamma2`	nonnegative regularization parameter for shrinking phases
`at`	prior vector
`max_iter`	maximum number of outer iterations for bcd
`verbose`	boolean flag; if TRUE diagnostic info is printed